The new A8 is one of the safest sedans in the luxury class. It protects its passengers in new, highly intelligent ways: with a high-strength body, adaptive restraint systems and the new Audi pre sense safety system. It is available in a standard version and in three expanded levels. When designing this system, Audi tapped into its broad knowledge base that it had created itself: The AARU (Audi Accident Research Unit) investigates real-world accidents and analyzes the relevant databases.
In the standard variant, Audi pre sense basic, the system utilizes the information from the ESP sensors. When they signal a critical situation, such as skidding or maximum braking, the control unit intervenes. Depending on the situation, it activates the hazard warning lights and closes the side windows and the sunroof; it also partly or fully tensions the front seat belts. Small electric motors trigger this process, which is reversible – if the situation is averted without an accident, the belts are released again. Audi pre sense tensions the front belts every time the car starts – so gently that it is almost imperceptible.
The expanded levels of the new safety system are called Audi pre sense front, Audi pre sense plus and Audi pre sense rear. They are networked in a pioneering manner with the optional assistance systems Audi adaptive cruise control with stop & go function and Audi side assist. This makes their actions more differentiated and powerful than those of competing systems.
In finely tuned interplay with ACC stop & go, Audi pre sense front affords additional protection against rear-end collisions with moving vehicles, and supports the driver in three stages. If the luxury sedan is approaching a slower moving car ahead, a warning gong sounds while a red signal lights up on the dashboard. Parallel to this, the brake system is prefilled and the air strut/damper suspension is set to hard. The warning – and that is the Audi philosophy – is intended to persuade the driver to brake himself or to make an avoidance maneuver, which is often the better strategy. At this point there is still plenty of time to do so.
If the person at the wheel remains passive, the acute warning is issued in stage 2 – a warning jolt produced by the rapid generation of pressure in the brake system and lasting approximately 0.5 seconds. The seatbelts are lightly tensioned at the same time. If the driver now depresses the pedal, the hydraulic brake assist system provides more powerful braking relative to the preceding vehicle. The fact that the system is already prefilled saves between 0.1 to 0.2 seconds, or more than seven meters (22.97 ft) at a speed of 130 km/h (80.78 mph).
Should the driver also ignore the warning jolt, the third stage is activated – autonomous partial braking that initially slows the A8 at a rate of 3 m/s2. At this stage it closes the windows and sunroof and activates the hazard warning lights.
Collision mitigation: reducing speed by as much as 40 km/h (24.85 mph)
If the sedan is equipped with Audi pre sense plus, which is the full version of Audi pre sense, a fourth stage follows. After the autonomous braking at a rate of 3 m/s2, the braking force is increased to 5 m/s2 if the driver remains passive and the belts are pulled tight. The last phase of braking with maximum deceleration begins about half a second before impact – at a time when a saving avoidance maneuver would no longer be possible. The force of the inevitable collision and its consequences are greatly reduced, for by impact the A8 has cut its speed by about 40 km/h (24.85 mph) – significantly more than the competition can.
Audi pre sense rear mitigates the consequences of a rear-end collision, computing in advance how severe the collision will be. Here, too, it closes the windows and sunroof and tensions the seat belts. If the A8 is equipped with seats with a memory function, the upper backrest and the headrest are moved into a position that protects the head against possible whiplash. In addition, the optional pneumatic side bolsters are filled with air to secure the driver’s torso.
Strong protection: crash safety
The new Audi A8 has a body that offers excellent protection against all types of collisions. The longitudinal members at the front end are made of extruded sections and high-strength castings. In the event of a front-end collision, four load paths on each side of the car absorb the forces. Two of these are located in the upper portions of the fenders, the others in the longitudinal members and the buffers installed in front of the subframe for the engine and the front axle. They process and distribute the forces optimally, and the other car involved in the accident also benefits from the homogeneous design of the A8 front end.
A crossmember manufactured out of a double-box section and bent into the shape of an omega provides additional protection for the passenger cell. The omega bracket, a new development from Audi, is located on a line with the footwells and diverts the forces into the floor and the A-pillars. The longitudinal members in the floor panel come together in the shape of an arrow below the rear bench seat. Together with the center tunnel they constitute the body’s strongest node.
Standing guard in the cabin is the adaptive restraint system, which is networked with Audi pre sense. It draws its own information from eight acceleration and pressure sensors, two each in the control unit, at the front of the car, in the C-pillars and in the doors. It intelligently manages the interplay between the airbags and the belt force limiters to offer outstanding protection to passengers of any size, with smaller persons benefiting in particular.
Sensors on the front seat rails detect how far forward or back the seat is positioned. Because the control unit then knows the approximate position of the passenger, it can ensure that optimal use is made of the distance over which the upper body is slowed by the belt and the airbag. Audi pre sense reduces this distance by roughly 10 centimeters (3.94 in) because the belts are tensioned before the crash occurs.
If a passenger is sitting close to an airbag – this is typically a smaller person – a portion of the air is quickly expelled via valves after the airbag inflates so that the head and chest are gathered in more gently by the airbag. In a hard crash or with large occupants who sit farther back, the valves remain closed longer. The variable belt force limiters are also designed to be adaptive. They control belt tension so that the load on the chest remains as low as possible. Bracing structures, energy-absorbing pads and crash-optimized pedals reduces loads on the feet and legs.
Rear-impact protection: the integral head restraint system
The structural design of the seats and headrests is an important element of safety design, especially in the case of a rear-end collision. These types of accidents frequently occur at traffic lights, usually with impact speeds between 15 and 50 km/h (9.32 and 31.07 mph). In such collisions, the seatback is accelerated to between 7 and 25 km/h (4.35 and 15.53 mph) within a tenth of a second. The integral head restraint system from Audi acts here to counter the risk of whiplash injuries.
Four side airbags in the backrests of the front seats and the outside rear seats stand at the ready to catch the pelvic area and chest of the occupants in the event of a side-impact collision. The head airbag system protects the head. Stretching from the A-pillar to the C-pillar, it opens like a curtain from the roof frame to the door sill and is filled extremely quickly by the gas generator.
The new A8 has three-point automatic seatbelts with tension limiters at all five seats. The rear seats are equipped with Isofix fixtures for installing child seats. Large beams in the rear protect the passenger cell; the rear wheels are braced against the side sills in the event of a collision. The spare wheel well, which contains technical components like the battery or the compressor for the air struts, is very robust thanks to its high percentage of fiberglass and the voids in its plastic structure. A wide strip of embedded aluminum makes it even stronger.
The new A8 satisfies all legal requirements for the protection of pedestrians in the event of a crash. A special foam between the front bumper and its crossmember makes the impact slightly easier on the knees. If the head should hit the engine hood, the sheet metal can deform over a wide range. The gap between it and the hard components in the engine compartment is large. The standard insurance category crash – a parking lot crash – has no major financial consequences. The aluminum crash boxes bolted in front of the crossmembers at both the front and at the rear of the car are relatively easy to replace.
The front and rear sensors remain undamaged in the event of a low-speed parking crash because they are cleverly integrated into the deformable covering of the bumpers. The radar sensors for the ACC stop & go function and the camera for the night vision assistant are deep inside their cavities.
The equipment, data and prices specified in this document refer to the model range offered in Germany. Subject to change without notice; errors and omissions excepted.